Apparatus for automatically adjusting the timing of ignition of an internal combustion engine to correspond with the engine speed

ABSTRACT

An apparatus for automatically adjusting the timing of ignition of an internal combustion engine by changes in centrifugal force caused by changes in the speed of the engine. The apparatus is particularly useful as a component of an automobile engine.

United States Patent Jean Henri Stellwagen Paris, France [21] Appl.No. 11,485

[72] Inventor [22] Filed I' elfl6, 1970 [45] Patented Oct. 19, 1971 [73] Assignee Societe Anonyme Pour IEquipement Electrique des Vehicules, S.E.V. Marchal Issy les Moulineaux, France [32] Priority Feb. 18, 1969, Aug. 12, 1969 [33] France [31] 69 04032 and 69 27755 [54] APPARATUS FOR AUTOMATICALLY ADJUSTING THE TIMING OF IGNITION OF AN INTERNAL COMBUSTION ENGINE TO CORRESPOND WITH THE ENGINE SPEED 9 Claims, I 1 Drawing Figs.

[52] U.S.Cl 123/1465 [51] Int. Cl F02p 5/06 [50] Field ofSearch 123/117, 117.1, 146.5 A; 200/19; 64/25 [56] References Cited UNITED STATES PATENTS 3,220,395 1l/1965 Julian et al 123/1465 A Primary Examiner- Laurence M. Goodridge Attorney- Plumley & Tyner ABSTRACT: An apparatus for automatically adjusting the timing of ignition of an internal combustion engine by changes in centrifugal force caused by changes in the speed of the engine. The apparatus is particularly useful as a component of an automobile engine.

PATENTEBUEI 19 I97! SHEET 1 BF 7 FIG.S

FIG. 1

INVENTOR JEAN HENRI STELLWAGEN BY FE ATTO RNE'YS PATENTEUUBI 191971 3.613.652

SHEET ESP 7 INVENTOR JEAN HENPJ STELLWAGEH BY v ' 3,613,652 PATENTEnnm mm mm W 7 FIG.3

wvavro JEAN sum STELLWAGEN ATTOKNE Y5 PATENTEDUBT 19 I97! SHEET 5 [IF 7 FIG. 7

INVENTOR JEAN HENRI 5TELLWAGEN BY PAM- HTTOENE'YS PATENTEDucI 19 I971 3.613.652

. SHEET SUF 7 IN VE NTOR JEAN HEN Rl STELLWAGEN BY M APPARATUS FOR AUTOMATICALLY ADJUSTING THE TIMING OF IGNITION OF AN INTERNAL COMBUSTION ENGINE TO CORRESPOND WITH THE ENGINE SPEED THE DISCLOSURE This invention relates to an ignition-timing device and more particularly it relates to such a device which adjusts the timing automatically to correspond to changes in the speed of the engrne.

It is known that for certain types of internal combustion engines it is necessary to apply the ignition spark to the gases introduced into the combustion chambers at a time different from that when maximum compression of the gases occurs. It is customary, in standard devices, to advance the spark by an inertial block device that is subject to centrifugal force, causing a movement of the control cam with reference to the breaker assembly of the ignition. It is known that for certain engines it is necessary at low r.p.m. to be able to retard the spark, the value being a function of the speed of the engine. Moreover, this delay may promote better gas combustion at low r.p.m. The present invention is intended to describe a device which employs an assembly of inertial blocks activated by centrifugal force, and which produces a retarding of the spark on the one hand for a certain speed range and on the other hand an advancing of the spark for a certain speed range. It is noteworthy that the device of the invention provides an association of elements that produces an advance of the spark corresponding to a given increase in engine r.p.m. with elements that produce a delay of the spark, all of which is rapidly established at a maximum value for a slight change of engine r.p.m.

The present invention relates to a new apparatus for ignition timing wherein the timing of the ignition point of gases in the combustion chamber is adjustedwith respect to the point of maximum compression of the gases in said combustion chamber. The device is driven in rotation synchronously with the engine to which it is associated and it incorporates a control shaft that is integral with a support plate, and a movable plate that is integral with a cam which is centered on the said shaft, and which cooperates with a breaker assembly containing the usual contacts which open and close to produce an ignition spark in the combustion chambers of the engine. The support plate carries two shafts which are parallel to the control shaft, and which serve respectively as pivots around which two primary inertial blocks are articulated. These primary inertial blocks partially enclose between their ends two rollers which are rigidly connected respectively to one end of one of a pair of secondary inertial blocks. Each of these secondary blocks is articulated at the other end about a shaft fixed to the movable plate and positioned parallel to the control shaft. The primary and secondary inertial blocks are so designed and positioned that a plane passing through their respective centers of gravity and through the central shaft can be rotated around the control shaft as an axis to a position where it passes through the two shafts which provide articulation of a pair of such blocks. The rollers move inside of oblong recesses in the movable plate and are restrained in movement by the action of at least two springs, one of which is rigidly connected to the support plate and the other to the movable plate.

In a preferred embodiment each primary inertial block is symmetrical and concave with respect to the control shaft, and has a pivot near the middle of the block with the end on either side of the pivot in contact with one of the rollers mentioned above. The secondary inertial blocks are also symmetrical wit reference to the control shaft of the device and they are disposed so as to enclose the primary inertial blocks. The oblong recesses of the movable plate, which restrict the movement of the shafts of the two rollers, are circular sectors that are symmetrical with reference to the control shaft and centered thereon, the angular opening of the said sectors being substantially equal to the maximum spark delay measured angularly. The shaft of each roller is attached to two springs rigidly connected with the support plate, one of said springs being attached to the roller shaft by a loop which engages the shaft only during a portion of the travel of the shaft. The springs associated to the two roller shafts are disposed on the side of the movable plate where there are no primary or secondary inertial blocks. The springs joined to'the support plate are attached on the one hand to the roller shaft and on the other hand to lugs that are integ'ral'with the support plate and parallel to the drive shaft of the device. The springs attached to the roller shafts and rigidly connected to the movable plate are sufficiently strong to prevent a movement of the secondary inertial blocks so long as the engine'r.p.m. does'not're'ach a specific value.

In a first modification, the secondary inertial blocks bear a magnet which insures that theyremain in contact with the primary inertial blocks so long as the centrifugal force exerted on the secondary blocks is less than the force of attraction of the magnet. The support plate is provided with stops which cooperate with the movable'plate and limit movement of the movable plate with respect to the support plate.

In a second modification,the inertial blocks are prevented from moving when the centrifugal force is low by the attraction force of a'n't'a'gnet which is rigidly attached to the secondary inertial block and cooperating with a magnetic piece adjustably attached to the movable plate to produce a gap therebetween. I

In another embodiment of this invention the secondary inertial blocks contain adjustable screw stops which cooperate with the primary inertial blocks to fix the respective positions of two cooperating blocks, the said screws being preferably substantially perpendicular to the axis of articulation of the inertial blocks.

Still another embodiment of this invention the secondary blocks each carry a magnet which exerts its force of attraction on an element that is rigidly attached to the movable plate of the ignition device, the distance between the element and the magnetbeing adjustable.

When the device of this invention is used for ignition of an internal combustion engine, the control shaft is generally driven by the engine, at a speed that is proportionate to that of the engine. When the engine r.p.m. is below a first threshold, the springs that are rigidly connected to the movable plate, possibly aided by magnets of the secondary inertial blocks, hold the said plate in the position that it occupies when the engine is not running. Beyond this first threshold, the secondary blocks move under the effect of centrifugal force and the rollers, being inserted between the primary blocks, play the role of fixed points for this displacement and cause the movable plate to rotate in a relative motion whichis reverse to the direction of rotation of the control shaft and in an amount which corresponds to a delay of the spark. When the engine r.p.m. of the device increases, the roller shaft comes into contact with one end of the oblong recesses of the movable plate, limiting the rotation of the said plate and holds the spark delay at that point as a maximum value. I

In the embodiment wherein the secondary inertial blocks contain adjustable stop screws that cooperate with the primary blocks as mentioned above, the effect of clearances between mating parts (play") play" can be eliminated and the maximum value of the delay that the device allows can be precisely regulated. In fact, when the components are assembled to produce the ignition device of this invention, there will be a certain amount of play between the primary and the secondary inertial blocks even though the machining of the components has been excellent. Adjustable stops that are rigidly afiixed to the secondary blocks are so positioned that the maximum possible angular travel for the secondary blocks, i.e. between the position when in contact with the above mentioned adjustable stop and the position at the extremity of the oblong recess of the movable plate, corresponds exactly to the angular value of maximum delay of ignition desired. Moreover, as also noted above, if each of the secondary inertial blocks has a magnet that prevents any movement relative to the movable plate until centrifugal force corresponding to a certain value of the r.p.m. is sufficient to overcome the force of attraction of the magnets, it will be understood that simple adjustments of the pieces on the movable plate that cooperate with the magnet will provide such variation as needed of the value of the r.p.m. in which a delay of ignition will be established. It is clear that when the adjustable stops that are rigidly connected to the secondary blocks have been adjusted as indicated, it is necessary, in order to overcome the attraction of the magnet at a specific r.p.m., to adjust the gap between the said magnet and the cooperating piece on the movable plate to which the magnetic force is directed. Once the initial position of the secondary inertial blocks is determined with reference to the entire device by reason of the presetting of the adjustable stops, adjustable magnetic pieces rigidly connected to the movable plate provide the possibility of adjusting the gap to the desired value corresponding to the value of the r.p.m. at which a delay of ignition is to be established.

When the engine r.p.m. increases to a second threshold, the primary inertial blocks move under the effect of centrifugal force despite the opposing force exerted by the first spring (i.e. without a loop) attached to the support plate. This movement of the primary inertial blocks causes a movement of the rollers and a movement of the movable plate in the direction reverse to that of the preceding movement of the movable plate. Consequently it causes a reduction of the delay of the spark. The movement of the primary blocks continues in this way until a third threshold of r.p.m. is reached. Beyond this third threshold the springs that are joined to the support plate and that have the delayed restraining action due to their attachment to roller shafts by a loop arrangement exert their effect when the rollers and the movable plate have moved to a predetermined location because of the increase in the engine r.p.m. When the movable plate finally reaches contact with the stops of the support plate, there is no further possibility of movement in that direction and this point corresponds to the maximum advance in ignition, or to the minimum delay in ignition wherein the rotation of advance would not have entirely compensated the initial delay rotation.

It is quite clear that the shafts of the roller can be provided with a plurality of springs with loop attachments, joined to the support plate, and also with a plurality of springs with or without loop attachments, joined to the movable plate. It is appropriate to note that the presence of these different springs which exert their restraining forces at different r.p.m. permit almost any desired characteristic in the delay and advance of ignition. It should be pointed out that the presence of a magnet joined to the secondary inertial blocks is important in that it allows accentuation of the suddenness of entrance into action of the said secondary blocks and consequently makes it possible, with very slight variation of the r.p.m. of the engine, to establish a very great delay of ignition.

In order better to understand the scope of this invention, two preferred embodiments will now be described with reference to the attached drawings. It is not intended that these embodiments shall be limitations on the invention, but rather that they are illustrative of its several variations.

In the attached drawings:

FIG. 1 is an axial cross section taken along I-I of FIG. 2, showing the ignition apparatus of this invention.

FIG. 2 is a plan view of the apparatus of this invention in a position that corresponds to operation at very low engine r.p.m., the movable plate being shown in dot-and-dash lines.

FIG. 3 is a view similar to that of FIG. 2 showing the same apparatus in a position that corresponds to a maximum ignition delay.

FIG. 4 is a view similar to that of FIG. 2 showing the same apparatus in a position corresponding to a maximum advance of ignition.

FIG. 5 is a graph showing angular variations of the ignition point as a function of engine r.p.m. in accordance with FIGS. [-4.

FIG. 6 is a schematic axial cross section taken along I-I of FIG. 7 showing a second embodiment of the ignition device of this invention.

FIG. 7'is a schematic plan view of the device of this invention in a position corresponding to the engine at rest, the movable plate being shown in dot-and-dash lines.

FIG. 8 is a plan view similar to that of FIG. 7 at the moment of maximum ignition delay.

FIG. 9 is a plan view similar to that of FIG. 7 at the moment of maximum advance of ignition.

FIG. 10 is a top view of the device with its movable plate.

FIG. 11 is a graph showing the angular variation of the ignition point as a function of the engine r.p.m. in accordance with FIGS. 6-10.

With reference to the drawings, more particluarly to FIGS. 15, the housing of the ignition device of the invention 1 is provided at its lower portion with a sleeve 2 inside which there is a control shaft 3. Case 1 is generally cylindrical, and control shaft 3 is disposed along the axis of case 1. Control shaft 3 is attached to support plate 4 disposed in the lower part of casing 1 perpendicular to control shaft 3. Around the upper part of control shaft 3 there is located a cam 5 whose lower part is affixed to movable plate 6. Cam 5 acts as a sleeve for the upper part of control shaft 3 and movable plate 6 is perpendicular to control shaft 3. Around cam 5 there is centered a breaker as sembly 7 whose point is in contact with the profile of cam 5 as is normal in ordinary ignition devices. In FIG. I there is shown only the low-voltage part of the ignition-timing device, it being understood that this part cooperates with a high-voltage distributor in the usual manner for standard ignition devices.

Support plate 4 supports two shafts 88b which are parallel to control shaft 3. Shafts 8a, 8b serve as pivotal supports respectively for articulating two primary inertial blocks 9a, 9b which are generally concave and symmetrically disposed with reference to control shaft 3. Shafts 8a, 8b are in the central zone OF blocks 9a, 9b. The planes that contain control shaft 3 and the centers of gravity of blocks 9a, 9b coincide respectively with the planes that include control shaft 3 and shafts 8a, 8b when that plane is rotated about control shaft 3 as an axis in the direction of rotation of control shaft 3. Between inertial blocks 9a, 9b there are two rollers 10a, 10b whose shafts 15a, 15 b are carried respectively on secondary inertial blocks Ila, 11b which are disposed symmetrically with respect to control shaft 3. Blocks 11a, 11b are formed of two elements which are substantially at right angles to each other, one of the said elements hearing at its end the roller 10a or 10 b that is associated with that block and the other element supporting at its end a pivotal shaft 12a or 12b for articulation. It is to be understood that components of the same number are similar and that components with the same letter cooperate with each other. Shafts 12a, 12b are rigidly fixed to movable plate 6. The planes which contain control shaft 3 and the centers of gravity of blocks 11a, 11b coincide respectively with the planes that contain control shaft 3 and shafts 22a, 12b when that plane is rotated around control shaft 3 as an axis in the direction of rotation of control shaft 3. Secondary inertial blocks 11a, 11b are positioned outside of primary inertial blocks 90, 9b. To allow free clearance of the primary blocks with respect to the secondary blocks, one of the arms fonned by blocks Ila, 11b is machined to provide an internal recess into which the primary blocks 9a, 9b can be fitted.

Support plate 4 carries stops 13a, 13b which cooperate with recesses 14a, 14b in movable plate 6. Shafts 15a, 15b rollers 10a, 10b extend above the upper surface of the movable plate 6 by passing through recesses 16a, 16b. Recesses 16a, 16b are in the form of a circular sector centered on control shafts 3 presenting a 20 angular opening.

Above movable plate 6 there are disposed, symmetrically with respect to control shaft 3, six springs 17a, 18a, 19a and 17b, 18b, 19b. Springs 18a, 18b are attached at one end to lugs 20a, 20b which are integral with support plate 4 and parallel to control shaft 3. Similarly, springs 19a 19b are attached at one end to lugs 21a, 21 b which are on support plate 4 and parallel to control shaft 3. The other end of springs 18a, 18b and of 19a, 19b is attached to shafts 15a, 15b. The attachment of springs 18a, 18b to shafts 15a, 15b is by means of a loop in the spring wire which extends beyond the shaft so as not to exert any force of the spring on the shaft until the shaft is moved to the end of the loop. The attachment of springs 19a, 19b on the said shafts is direct i.e. without a loop. Springs 17a, 17b are attached at one end to shafts 15a, 15b and at the other end to lugs 22a, 22b of movable plate 6, the attachment of the said springs to shafts 15a and 15b being direct, i.e. without a loop.

The secondary inertial blocks 11a, llb carry magnets 23a, 23b placed near the pivotal shafts 12a, 12b on the face that is opposite the thick part of primary blocks 9a, 9b. The form of blocks 90, 9b and of blocks 11a, 11b is such that there can be contact respectively between magnets 23a, 23b and blocks 9b, 9a.

An arrow indicates the direction of rotation of control shaft 3. For an r.p.m. in the range of points 24, 25 of the curve of FIG. 5, the force of springs 17a, 17b and the attraction of magnets 23a, 23b is such that any movement of secondary blocks 1 la, llb by reason of centrifugal force is prevented. Similarly, the force of springs 19a, l9bis sufiicient to prevent any movement of primary blocks 9 a, 1. As a consequence, the whole of the device of the invention is driven by control shaft 3 without there being any relative motion of movable plate 6 and cam 5 with respect to support plate 4 and control shaft 3.

When the r.p.m. corresponding to point 25 is reached, the centrifugal force exerted on blocks 11a, 11b is sufficient to cause a movement of these blocks. This movement is produced about shafts 15a, 15b which are held in position between primary blocks 9a, 9b which, in turn, are motionless with respect to support plate 4. The result of the forces is that shafts 12a, 12b tend to move away from control shaft 3, causing a rotation of movable plate 6 in the direction reverse to the rotation of control shaft 3. This produces a delay of ignition because cam 5 is moved in a direction opposite that of the direction or rotation of control shaft 3. As the r.p.m. increases this movement continues until shafts 15a, l5come into contact with one end of recesses 16a, 16b. At this point the movement of blocks 11a, llb by reason of centrifugal force is stopped. The maximum spark delay is thus obtained, corresponding to point 26 of FIG. 5. The presence of magnets 23a, 23b makes it possible to obtain a very steep curve between points 25 and 26, i.e. it permits, for a slight variation of r.p.m. a change from zero delay to maximum delay. The position of the component parts of the device of this invention at maximum delay is represented in FIG. 3.

If the r.p.m. of control shaft 3 continues to be increased, primary inertial blocks 9a, 9b begin to separate due to the fact that the centrifugal force exerted on them becomes sufficient to overcome the force of springs 19a, 19b. This movement of blocks 9a, 9b causes rotation of rollers a, 10b about control shaft 3, in the same direction as the direction of rotation of control shaft 3. Since shafts a, 15b bear against one end of recesses 16a, 16b, the driving of the rollers causes the movement of movable plate 6 and the rotation of cam 5. This movement corresponds to an advance of the spark, or more exactly, at the start of themovement to a reduction of the originally established delay of ignition. The start of this movement corresponds to point 27 of the graph of FIG. 5 and the rotation of plate 6 is shown on the graph by a straight segment 27, 28 whose angle of inclination is a function of the force of springs 19a, 1%.

When the r.p.m. is increased to that corresponding to point 28 on the graph, shafts 15a, 15b come into contact with the ends of the loops of springs 18a, 18b thus causing those springs to add their restraining forces to those exerted by springs 19a, 19b. Consequently the rate of increase of the advance of the spark is effected less rapidly than before. This phase of operation is represented by the segment 28, 29 in the graph of FIG. 5.

When the r.p.m. is increased to that corresponding to point 29 of FIG. 5, recesses 14a, 14b of movable plate 6 come into contact with stops 13a, 13b on support plate 4. This stops any further relative movement between the two plates and consequently there is attained the maximum advance which remains constant even though the r.p.m. might increase. This phase of operation is shown as segment 29, 30 of the curve of FIG. 5. The position of the component parts of the device of this invention at the point of maximum advance is shown in FIG. 4.

It is to be noted that the amount of maximum delay that can be attained is a function of the angular opening of recesses 16a, 16b of movable plate 6. In the preferred embodiment the opening is about 20, and maximum delay that is obtained is also about 20. The length of segment 26, 27 and the configuration of curve 27, 28, 29, 30 are, for the most part, functions of the characteristics of springs 17a, 18a, 19a and 17b, 18b, 19 b.

A second embodiment of the device of the invention will now be described, in which embodiment the magnets of the secondary inertial blocks cooperate with magnetic pieces fastened to the movable plate, and in which the secondary inertial blocks contain adjustable stop screws which cooperate to set the relative positions of the two types of blocks. The drawings which correspond to this'second embodiment are FIGS. 6 to 11. All the component parts which are numbered 1 through 22 are identical to those described with reference to FIGS. l-S.

In this second embodiment, the secondary inertial blocks 11a, llb carry, respectively, magnets 32a, 32b, positioned near the right angle formation of the block and slightly above its upper surface. Magnets 32a, 32b oppose two adjustable magnetic pieces 30a, 30b which are screwed to movable plate 6. In the body of the secondary blocks lla, llb between magnets 32a, 32b and shafts 12a, 12b respectively, there are located two adjustable stops 31a, 31b which are screwedinto the blocks in such a fashion that the end of the screw stops comes into contact with primary blocks 90, 9b. Stops 31a, 31b are perpendicular to control shaft 3.

Generally, when the device of this invention is initially installed there is a certain amount of play between primary blocks 9a, 9b and secondary blocks 11a, llb and frequently rollers 10a, 10b are unable to reach the extremities of recesses 16a, 16b because of imprecise machining. These recesses are designed to have an angular opening of about 20 but the angle may not be made with great precision.

Stops 31a, 31b are adjusted with respect to their location so as to eliminate the play that initially exists between the primary and secondary blocks. Furthermore, it will be realized that the maximum ignition delay that can be attained through this device is a function of the possible angular travel for secondary blocks 11a, llb. This angular travel is measured between the extreme position of the blocks, i.e. from contact with stops 31a, 31b to their position when rollers 10a, 10b reach the extremities of recesses 16a, 16b. Therefore by adjusting screw stops 31a, 31b it is possible to bring the angular travel of blocks 11a, 11b to the desired value for maximum delay, which determines the position of points 36, 37 of the graph of FIG. 11. Since this adjustment is provided independently for each of the blocks 11a, 11 b, it is possible, despite imperfections of machining, to make the movements of the two blocks 11a, 11 b perfectly symmetrical, so that they simultaneously reach the extremities of recesses 16a, 16b.

In a second stage, when the position of stops 31a, 31b has been adjusted, pieces 30a, 30b can be positioned by their fixing screws, so as to obtain the desired gap between these pieces and magnets 32a, 32b with which they cooperate. The size of this gap determines the initial force of attraction exerted by magnets 32a, 32b on the said pieces, i.e. the restraining force exerted on secondary blocks lla, llb opposing the effect of centrifugal force at low r.p.m. Thus, by adjustment of the gap between mag-nets 32a, 32b and pieces 30 0, 30b the position of point 35 of the graph of FIG. 11 is determined. When stops 31a, 31b have been finally positioned the adjusting screws can be cut flush with the edge of blocks Ila, 1 lb to make it impossible to accidentally change the setting.

An arrow in the drawing indicates the direction of rotation of control shaft 3. For r.p.m. corresponding to points 34 35 of the curve of FIG. 11, the force of springs 17a, 17b and the attraction of magnets 32a, 32b are such that all movement of secondary blocks lla, 11b due to centrifugal force is prevented. Similarly, the force of springs 19a, 19b is sufficient to prevent any movement of primary blocks 9a, 9b. As a result, the whole of the device of the invention is driven by control shaft 3 without any relative movement of movable plate 6 and cam 5 with reference to support plate 4 and control shaft 3.

When an r.p.m. is reached which corresponds to point 35 of FIG. 11, the centrifugal force exerted on blocks 11a, 11b is sufficient to cause the said blocks to move. This movement is produced about shafts 15a, 15b which are held in position between primary blocks 9a, 9b which, in turn, remain motionless with respect to support plate 4. By reason of this movement, shafts 12a, 12b tend to move away from control shaft 3, which causes a rotation of movable plate 6 in the direction opposite to that of the rotation of control shaft 3. Thus, there is a delay in ignition, since cam 5 is carried in a direction opposite to that of rotation of control shaft 3. This movement continues until the r.p.m. increases to the point at which shafts 15a, 15b are stopped by the ends of recesses 16a, 16b. At this moment, the movement of blocks 11a, 1 lb under the effect of centrifugal force is effectively stopped. Maximum ignition delay is thus attained, corresponding to point 36 of FIG. 1 l. The initial setting of stops 31a, 31b permits one to limit the angular travel of blocks 11a, 11b and to fix the position of segment 36 37 of the curve of FIG. 11 at the desired value. The presence of magnets 32a, 32b provides the very steep slope between points 35 and 36, i.e. it makes it possible with slight variation of the r.p.m. to pass from zero delay to maximum delay. The maximum delay position is shown in FIG. 8.

If the r.p.m. of control shaft 3 continues to increase, primary blocks 9a, 9b begin to separate because the centrifugal force exerted on them becomes sufficient to overcome the force of springs 19a, 19b. This movement of blocks 9a, 9b causes rotation of rollers 10a, 10b, around control shaft 3, in the same direction as the direction of rotation of control shaft 3. Since shafts a, 15b are in contact with one end of recesses 16a, 16b the driving of the rollers causes movement of movable plate 6 and consequently rotation of cam 5. This movement corresponds to an advance of ignition, or more exactly, at the start of the movement, to a reduction of the initially established ignition delay. The start of this movement corresponds to point 37 on the graph of FIG. 11, and the rotation of movable plate 6 is expressed on the graph by a segment 37 38 whose slope is a function of the force of springs 19a, 19b.

When the r.p.m. corresponding to point 38 of the graph is reached, shafts 15a, 15b come into contact with the ends of the loops of springs 18a, 18b causing these springs to add their restraining force to that exerted by springs 19a, 19b. As a result the increase of spark advance is effected less rapidly than before. This phase of operation is represented by segment 38 39 in the graph of FIG. 11.

When the r.p.m. is attained which corresponds to point 39 of FIG. 11, elements 14a, 14b of movable plate 6 come into contact with stops 13a, 13b of support plate 4. This prevents any further relative motion between the two plates, and consequently this represents the maximum advance, which remains constant even if the r.p.m. increases. This phase of operation is indicated by segment 39 40 of the curve of FIG. 11. The position of the component parts of the device of this invention at the moment of maximum advance is shown in FIG. 9.

It is understood of course that the embodiments described above are not limitative in any way and could be modified as desired without exceeding the scope of the invention.

What is claimed is:

1. An ignition device for an internal combustion engine which automatically adjusts itself by centrifugal force to set the timing of ignition of the gases to correspond with the speed of the engine comprising a control shaft being driven in rotatron sync ronously with the said engine and rigidly attached to a support plate; a movable plate rigidly attached to a cam centered on but not attached to said shaft; a breaker assembly centered around and cooperating with said cam to cause opening and closing of contacts which in turn cause ignition in the combustion chambers of said engine; two shafts rigidly attached to said support plate and positioned parallel to said control shaft, each of said shafts having rotatably attached thereto an arcuate primary inertial block which cooperates with two rollers each of which is mounted on a separate roller shaft parallel to said control shaft and attached to one end of one of a pair of secondary inertial blocks rotatably attached at its other end to a shaft mounted on said movable plate in a position parallel to said control shaft; each of said primary inertial blocks being in contact with both of said rollers, each roller being in rolling contact with the inside concave surface of one of said primary blocks and also in nonrolling contact with a notch at the end at the other of said primary blocks; said primary and secondary blocks being disposed symmetrically about said control shaft such that a plane containing said control shaft and the centers of gravity of said blocks can be rotated around said control shaft as an axis and in the direction of rotation of said control shaft to a position where that plane contains the pair of said shafts about which the corresponding pair of said inertial blocks rotate, said roller shaft being limited in movement around said control shaft by an oblong recess in said movable plate and being restrained from movement within said recess by at least two springs one of which is joined to said support plate and the other of which is joined to said movable plate.

2. The device of claim 1, wherein said secondary blocks are symmetrical with respect to said control shaft of the device and disposed so as to enclose said primary blocks between them.

3. The device of claim 1, wherein said oblong recesses in said movable plate are circular sectors which are symmetrical with respect to said control shaft and centered thereon, the angular opening of the said sectors being substantially equal to the maximum ignition delay measured angularly.

4. The device of claim I, wherein each of said roller shafts is restrained in movement by two springs attached to said support plate, one of said springs providing movement restraint at any position of said shaft while the other of said springs provides such restraint only after an initial movement of said shaft.

5. The device of claim 1 wherein said springs attached to said roller shafts are sufficiently strong to restrain movement of said secondary blocks until the speed of said control shaft reaches a predetermined value.

6. The device of claim 1, wherein each of said secondary blocks supports a magnet which is sufficiently strong to prevent said primary blocks from moving separately from said secondary blocks until the centrifugal force exerted on the said secondary blocks by the rotational speed of said control shaft is sufficient to overcome the attraction of the magnet.

7. The device of claim 1, wherein said support plate contains means to limit the movement of said movable plate with respect to said support plate.

8. The device of claim 1, wherein said secondary blocks contain adjustable screw stops which provide a means for adjusting the relative positions of said secondary blocks with respect to said primary blocks when they were in contact with each other.

9. The device of claim 1, wherein each of said secondary blocks contains a magnet which cooperates with an element attached to said movable plate to provide an adjustable gap therebetween, said gap being adjusted to the necessary size to restrain movement of said secondary blocks until a predetermined speed of said control shaft is reached. 

1. An ignition device for an internal combustion engine which automatically adjusts itself by centrifugal force to set the timing of ignition of the gases to correspond with the speed of the engine comprising a control shaft being driven in rotation synchronously with the said engine and rigidly attached to a support plate; a movable plate rigidly attached to a cam centered on but not attached to said shaft; a breaker assembly centered around and cooperating with said cam to cause opening and closing of contacts which in turn cause ignition in the combustion chambers of said engine; two shafts rigidly attached to said support plate and positioned parallel to said control shaft, each of said shafts having rotatably attached thereto an arcuate primary inertial block which cooperates with two rollers each of which is mounted on a separate roller shaft parallel to said control shaft and attached to one end of one of a pair of secondary inertial blocks rotatably attached at its other end to a shaft mounted on said movable plate in a position parallel to said control shaft; each of said primary inertial blocks being in contact with both of said rollers, each roller being in rolling contact with the inside concave surface of one of said primary blocks and also in nonrolling contact with a notch at the end at the other of said primary blocks; said primary and secondary blocks being disposed symmetrically about said control shaft such that a plane containing said control shaft and the centers of gravity of said blocks can be rotated around said control shaft as an axis and in the direction of rotation of said control shaft to a position where that plane contains the pair of said shafts about which the corresponding pair of said inertial blocks rotate, said roller shaft being limited in movement around said control shaft by an oblong recess in said movable plate and being restrained from movement within said recess by at least two springs one of which is joined to said support plate and the other of which is joined to said movable plate.
 2. The device of claim 1, wherein said secondary blocks are symmetrical with respect to said control shaft of the device and disposed so as to enclose said primary blocks between them.
 3. The device of claim 1, wherein said oblong recesses in said movable plate are circular sectors which are symmetrical with respect to said control shaft and centered thereon, the angular opening of the said sectors being substantially equal to the maximum ignition delay measured angularly.
 4. The device of claim 1, wherein each of said roller shafts is restrained in movement by two springs attached to said support plate, one of said springs providing movement restraint at any position of said shaft while the other of said springs provides such restraint only after an initial movement of said shaft.
 5. The device of claim 1 wherein said springs attached to said roller shafts are sufficiently strong to restrain movement of said secondary blocks until the speed of said control shaft reaches a predetermined value.
 6. The device of claim 1, wherein each of said secondary blocks supports a magnet which is sufficiently strong to prevent said primary blocks from moving separately from said secondary blocks until the centrifugal force exerted on the said secondary blocks by the rotational speed of said control shaft is sufficient to overcome the attraction of the magnet.
 7. The device of claim 1, wherein said support plate contains means to limit the movement of said movable plate with respect to said support plate.
 8. The device of claim 1, wherein said secondary blocks contain adjustable screw stops which provide a means for adjusting the relative positions of said secondary blocks with respect to said primary blocks when they were in contact with each other.
 9. The device of claim 1, wherein each of said secondary blocks contains a magnet which cooperates with an element attached to said movable plate to provide an adjustable gap therebetween, said gap being adjusted to the necessary size to restrain movement of said secondary blocks until a predetermined speed of said control shaft is reached. 